KR20210154727A - Method and apparatus for performing random access procedure for coverage enhancement - Google Patents

Abstract

Embodiments of the present invention relate to a method and apparatus for performing a random access procedure for coverage enhancement. An embodiment of the present invention relates to a method, in a method for a terminal to perform a random access procedure for coverage enhancement, which includes the steps of: transmitting a random access channel preamble for repeated transmission of Msg3 through a physical random access channel; receiving a random access response including uplink scheduling information for the repeated transmission of Msg3; and repeatedly transmitting Msg3 based on the uplink scheduling information.

Description

METHOD AND APPARATUS FOR PERFORMING RANDOM ACCESS PROCEDURE FOR COVERAGE ENHANCEMENT

The present embodiments propose a method and apparatus for performing a random access procedure for coverage extension in a next-generation radio access network (hereinafter referred to as "New Radio [NR]").

3GPP recently approved "Study on New Radio Access Technology", a study item for research on next-generation radio access technology (that is, 5G radio access technology), and based on this, RAN WG1 for NR (New Radio) Designs for a frame structure, channel coding & modulation, waveform & multiple access scheme, and the like are in progress. NR is required to be designed to satisfy various QoS requirements required for each segmented and detailed usage scenario as well as an improved data rate compared to LTE.

As representative usage scenarios of NR, eMBB (enhancement Mobile BroadBand), mMTC (massive machine type communication), and URLLC (Ultra Reliable and Low Latency Communications) have been defined. design is required.

Since each service requirement (usage scenario) has different requirements for data rates, latency, reliability, coverage, etc., through the frequency band constituting an arbitrary NR system As a method to efficiently satisfy the needs of each usage scenario, different numerology (eg, subcarrier spacing, subframe, TTI (Transmission Time Interval), etc.) based There is a need for a method for efficiently multiplexing a radio resource unit of

As part of this aspect, a design for coverage extension in the random access procedure is required.

Embodiments of the present disclosure may provide a specific method and apparatus capable of extending coverage by repeatedly transmitting Msg3 in a random access procedure in NR.

In one aspect, the present embodiments provide a method for a UE to perform a random access procedure for coverage extension, using a RACH Preamble for repeated transmission of Msg3 as a Physical Random Access Channel (PRACH). ), receiving a random access response (RAR) including uplink scheduling information for repeated transmission of Msg3, and repeatedly transmitting Msg3 based on the uplink scheduling information. can provide a way to

In another aspect, the present embodiments provide a method for a base station to perform a random access procedure for coverage extension, a physical random access channel (PRACH) for a random access channel preamble for repeated transmission of Msg3 ), transmitting a random access response (RAR) including uplink scheduling information for repeated transmission of Msg3, and repeatedly receiving the Msg3 based on the uplink scheduling information. methods can be provided.

In another aspect, the present embodiments provide a physical random access channel (PRACH) with a random access channel preamble for repeated transmission of Msg3 in a terminal performing a random access procedure for coverage extension. A transmitter for transmitting through Msg3, a receiver for receiving a random access response (RAR) including uplink scheduling information for repeated transmission of Msg3, and a controller for controlling operations of the transmitter and the receiver, wherein the transmitter includes an uplink It is possible to provide a terminal that repeatedly transmits Msg3 based on the link scheduling information.

In another aspect, the present embodiments provide a physical random access channel (PRACH) with a random access channel preamble for repeated transmission of Msg3 in a base station performing a random access procedure for coverage extension. A receiver for receiving through Msg3, a transmitter for transmitting a random access response (RAR) including uplink scheduling information for repeated transmission of Msg3, and a controller for controlling operations of the transmitter and receiver, the receiver includes It is possible to provide a base station that repeatedly receives Msg3 based on the link scheduling information.

According to the present embodiments, it is possible to provide a specific method and apparatus capable of extending coverage by repeatedly transmitting Msg3 in a random access procedure in NR.

1 is a diagram schematically illustrating a structure of an NR wireless communication system to which this embodiment can be applied.
2 is a diagram for explaining a frame structure in an NR system to which this embodiment can be applied.
3 is a diagram for explaining a resource grid supported by a radio access technology to which this embodiment can be applied.
4 is a diagram for explaining a bandwidth part supported by a radio access technology to which the present embodiment can be applied.
5 is a diagram exemplarily illustrating a synchronization signal block in a radio access technology to which the present embodiment can be applied.
6 is a diagram for explaining a random access procedure in a radio access technology to which this embodiment can be applied.
7 is a diagram for explaining CORESET.
8 is a diagram illustrating an example of symbol level alignment among different SCSs in different SCSs to which this embodiment can be applied.
9 is a diagram illustrating a conceptual example of a bandwidth part to which the present embodiment can be applied.
10 is a diagram illustrating a procedure in which a terminal performs a random access procedure for coverage extension according to an embodiment.
11 is a diagram illustrating a procedure in which a base station performs a random access procedure for coverage extension according to an embodiment.
12 is a diagram showing the configuration of a terminal according to another embodiment.
13 is a diagram showing the configuration of a base station according to another embodiment.

Hereinafter, some embodiments of the present disclosure will be described in detail with reference to exemplary drawings. In adding reference numerals to components of each drawing, the same components may have the same reference numerals as much as possible even though they are indicated in different drawings. In addition, in describing the present embodiments, if it is determined that a detailed description of a related well-known configuration or function may obscure the gist of the present technical idea, the detailed description may be omitted. When "includes", "having", "consisting of", etc. mentioned in this specification are used, other parts may be added unless "only" is used. When a component is expressed in the singular, it may include a case in which the plural is included unless otherwise explicitly stated.

In addition, in describing the components of the present disclosure, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only for distinguishing the elements from other elements, and the essence, order, order, or number of the elements are not limited by the terms.

In the description of the positional relationship of the components, when it is described that two or more components are "connected", "coupled" or "connected", two or more components are directly "connected", "coupled" or "connected" It should be understood that, however, two or more components and other components may be further “interposed” and “connected,” “coupled,” or “connected.” Here, other components may be included in one or more of two or more components that are “connected”, “coupled” or “connected” to each other.

In the description of the temporal flow relationship related to the components, the operation method or the production method, for example, the temporal precedence relationship such as "after", "after", "after", "before", etc. Alternatively, when a flow precedence relationship is described, it may include a case where it is not continuous unless "immediately" or "directly" is used.

On the other hand, when numerical values or corresponding information (eg, level, etc.) for a component are mentioned, even if there is no separate explicit description, the numerical value or the corresponding information is based on various factors (eg, process factors, internal or external shock, Noise, etc.) may be interpreted as including an error range that may occur.

A wireless communication system in the present specification refers to a system for providing various communication services such as voice and data packets using radio resources, and may include a terminal, a base station, or a core network.

The present embodiments disclosed below may be applied to a wireless communication system using various wireless access technologies. For example, the present embodiments are CDMA (code division multiple access), FDMA (frequency division multiple access), TDMA (time division multiple access), OFDMA (orthogonal frequency division multiple access), SC-FDMA (single carrier frequency division multiple access) Alternatively, it may be applied to various radio access technologies such as non-orthogonal multiple access (NOMA). In addition, the wireless access technology may mean not only a specific access technology, but also a communication technology for each generation established by various communication consultation organizations such as 3GPP, 3GPP2, WiFi, Bluetooth, IEEE, and ITU. For example, CDMA may be implemented with a radio technology such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA may be implemented with a radio technology such as global system for mobile communications (GSM)/general packet radio service (GPRS)/enhanced datarates for GSM evolution (EDGE). OFDMA may be implemented with a radio technology such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, and evolved UTRA (E-UTRA). IEEE 802.16m is an evolution of IEEE 802.16e, and provides backward compatibility with a system based on IEEE 802.16e. UTRA is part of the universal mobile telecommunications system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of evolved UMTS (E-UMTS) that uses evolved-UMTSterrestrial radio access (E-UTRA), and employs OFDMA in the downlink and SC- FDMA is employed. As such, the present embodiments may be applied to currently disclosed or commercialized radio access technologies, or may be applied to radio access technologies currently under development or to be developed in the future.

On the other hand, the terminal in the present specification is a comprehensive concept meaning a device including a wireless communication module that performs communication with a base station in a wireless communication system, WCDMA, LTE, NR, HSPA and IMT-2020 (5G or New Radio), etc. It should be interpreted as a concept including all of UE (User Equipment), MS (Mobile Station), UT (User Terminal), SS (Subscriber Station), wireless device, etc. in GSM. In addition, the terminal may be a user's portable device such as a smart phone depending on the type of use, and in a V2X communication system may mean a vehicle, a device including a wireless communication module in the vehicle, and the like. In addition, in the case of a machine type communication (Machine Type Communication) system, it may mean an MTC terminal, an M2M terminal, a URLLC terminal, etc. equipped with a communication module to perform machine type communication.

A base station or cell of the present specification refers to an end that communicates with a terminal in terms of a network, a Node-B (Node-B), an evolved Node-B (eNB), gNode-B (gNB), a Low Power Node (LPN), Sector, site, various types of antennas, base transceiver system (BTS), access point, point (eg, transmission point, reception point, transmission/reception point), relay node ), mega cell, macro cell, micro cell, pico cell, femto cell, RRH (Remote Radio Head), RU (Radio Unit), small cell (small cell), such as a variety of coverage areas. In addition, the cell may mean including a BWP (Bandwidth Part) in the frequency domain. For example, the serving cell may mean the Activation BWP of the UE.

In the various cells listed above, since there is a base station controlling one or more cells, the base station can be interpreted in two meanings. 1) in relation to the radio area, it may be the device itself providing a mega cell, a macro cell, a micro cell, a pico cell, a femto cell, or a small cell, or 2) may indicate the radio area itself. In 1), the devices providing a predetermined radio area are controlled by the same entity, or all devices interacting to form a radio area cooperatively are directed to the base station. A point, a transmission/reception point, a transmission point, a reception point, etc. become an embodiment of a base station according to a configuration method of a wireless area. In 2), the radio area itself in which signals are received or transmitted from the point of view of the user terminal or the neighboring base station may be indicated to the base station.

In the present specification, a cell is a component carrier having a coverage of a signal transmitted from a transmission/reception point or a coverage of a signal transmitted from a transmission/reception point (transmission point or transmission/reception point), and the transmission/reception point itself. can

The uplink (Uplink, UL, or uplink) refers to a method of transmitting and receiving data by the terminal to the base station, and the downlink (Downlink, DL, or downlink) refers to a method of transmitting and receiving data to the terminal by the base station do. Downlink may mean a communication or communication path from a multi-transmission/reception point to a terminal, and uplink may mean a communication or communication path from a terminal to a multi-transmission/reception point. In this case, in the downlink, the transmitter may be a part of multiple transmission/reception points, and the receiver may be a part of the terminal. In addition, in the uplink, the transmitter may be a part of the terminal, and the receiver may be a part of the multi-transmission/reception point.

The uplink and downlink transmit and receive control information through a control channel such as a Physical Downlink Control CHannel (PDCCH), a Physical Uplink Control CHannel (PUCCH), etc. Data is transmitted and received by configuring the same data channel. Hereinafter, a situation in which signals are transmitted/received through channels such as PUCCH, PUSCH, PDCCH, and PDSCH may be expressed in the form of 'transmitting and receiving PUCCH, PUSCH, PDCCH and PDSCH'.

For clarity of explanation, the present technical idea will be mainly described below for the 3GPP LTE/LTE-A/NR (New RAT) communication system, but the present technical characteristics are not limited to the corresponding communication system.

In 3GPP, after research on 4G (4th-Generation) communication technology, 5G (5th-Generation) communication technology is developed to meet the requirements of ITU-R's next-generation wireless access technology. Specifically, 3GPP develops LTE-A pro, which improved LTE-Advanced technology to meet the requirements of ITU-R as a 5G communication technology, and a new NR communication technology separate from 4G communication technology. LTE-A pro and NR both refer to 5G communication technology. Hereinafter, 5G communication technology will be described focusing on NR unless a specific communication technology is specified.

In the NR operation scenario, various operation scenarios were defined by adding consideration of satellites, automobiles, and new verticals to the existing 4G LTE scenarios. It is deployed in a range and supports the mMTC (Massive Machine Communication) scenario that requires a low data rate and asynchronous connection, and the URLLC (Ultra Reliability and Low Latency) scenario that requires high responsiveness and reliability and supports high-speed mobility. .

To satisfy this scenario, NR discloses a wireless communication system to which a new waveform and frame structure technology, low latency technology, mmWave support technology, and forward compatible technology are applied. In particular, in the NR system, various technological changes are presented in terms of flexibility in order to provide forward compatibility. The main technical features of NR will be described with reference to the drawings below.

<Normal NR system>

1 is a diagram schematically illustrating a structure of an NR system to which this embodiment can be applied.

1, the NR system is divided into a 5G Core Network (5GC) and an NR-RAN part, and the NG-RAN controls the user plane (SDAP/PDCP/RLC/MAC/PHY) and UE (User Equipment) It consists of gNBs and ng-eNBs that provide planar (RRC) protocol termination. gNB interconnection or gNB and ng-eNB interconnect via Xn interface. gNB and ng-eNB are each connected to 5GC through the NG interface. 5GC may be configured to include an Access and Mobility Management Function (AMF) in charge of a control plane such as terminal access and mobility control functions, and a User Plane Function (UPF) in charge of a control function for user data. NR includes support for both the frequency band below 6 GHz (FR1, Frequency Range 1) and the frequency band above 6 GHz (FR2, Frequency Range 2).

gNB means a base station that provides NR user plane and control plane protocol termination to a terminal, and ng-eNB means a base station that provides E-UTRA user plane and control plane protocol termination to a terminal. The base station described in this specification should be understood as encompassing gNB and ng-eNB, and may be used as a meaning to refer to gNB or ng-eNB separately if necessary.

<NR Waveform, Pneumologic and Frame Structure>

In NR, a CP-OFDM waveform using a cyclic prefix is used for downlink transmission, and CP-OFDM or DFT-s-OFDM is used for uplink transmission. OFDM technology is easy to combine with MIMO (Multiple Input Multiple Output), and has advantages of using a low-complexity receiver with high frequency efficiency.

On the other hand, in NR, since the requirements for data rate, delay rate, coverage, etc. are different for each of the three scenarios described above, it is necessary to efficiently satisfy the requirements for each scenario through the frequency band constituting an arbitrary NR system. . To this end, a technique for efficiently multiplexing a plurality of different numerology-based radio resources has been proposed.

Specifically, NR transmission numerology is determined based on sub-carrier spacing and cyclic prefix (CP), and the μ value is used as an exponential value of 2 based on 15 kHz as shown in Table 1 below. is changed negatively.

μ subcarrier spacing Cyclic prefix Supported for data Supported for synch 0 15 Normal Yes Yes One 30 Normal Yes Yes 2 60 Normal, Extended Yes No 3 120 Normal Yes Yes 4 240 Normal No Yes

As shown in Table 1 above, the NR numerology can be divided into five types according to the subcarrier spacing. This is different from the fact that the subcarrier interval of LTE, one of the 4G communication technologies, is fixed to 15 kHz. Specifically, subcarrier intervals used for data transmission in NR are 15, 30, 60, and 120 kHz, and subcarrier intervals used for synchronization signal transmission are 15, 30, 120 and 240 kHz. In addition, the extended CP is applied only to the 60 kHz subcarrier interval. On the other hand, as for the frame structure in NR, a frame having a length of 10 ms is defined, which is composed of 10 subframes having the same length of 1 ms. One frame can be divided into half frames of 5 ms, and each half frame includes 5 subframes. In the case of a 15 kHz subcarrier interval, one subframe consists of one slot, and each slot consists of 14 OFDM symbols. 2 is a diagram for explaining a frame structure in an NR system to which this embodiment can be applied.

Referring to FIG. 2 , a slot is fixedly composed of 14 OFDM symbols in the case of a normal CP, but the length of the slot in the time domain may vary according to the subcarrier interval. For example, in the case of a numerology having a 15 kHz subcarrier interval, the slot is 1 ms long and is configured with the same length as the subframe. On the other hand, in the case of numerology having a 30 kHz subcarrier interval, a slot consists of 14 OFDM symbols, but two slots may be included in one subframe with a length of 0.5 ms. That is, the subframe and the frame are defined to have a fixed time length, and the slot is defined by the number of symbols, so that the time length may vary according to the subcarrier interval.

Meanwhile, NR defines a basic unit of scheduling as a slot, and also introduces a mini-slot (or a sub-slot or a non-slot based schedule) in order to reduce transmission delay in a radio section. When a wide subcarrier interval is used, the length of one slot is shortened in inverse proportion, so that transmission delay in a radio section can be reduced. The mini-slot (or sub-slot) is for efficient support of the URLLC scenario and can be scheduled in units of 2, 4, or 7 symbols.

Also, unlike LTE, NR defines uplink and downlink resource allocation at a symbol level within one slot. In order to reduce the HARQ delay, a slot structure capable of transmitting HARQ ACK/NACK directly within a transmission slot has been defined, and this slot structure will be described as a self-contained structure.

NR is designed to support a total of 256 slot formats, of which 62 slot formats are used in 3GPP Rel-15. In addition, a common frame structure constituting an FDD or TDD frame is supported through a combination of various slots. For example, a slot structure in which all symbols of a slot are set to downlink, a slot structure in which all symbols are set to uplink, and a slot structure in which downlink symbols and uplink symbols are combined are supported. In addition, NR supports that data transmission is scheduled to be distributed in one or more slots. Accordingly, the base station may inform the terminal whether the slot is a downlink slot, an uplink slot, or a flexible slot using a slot format indicator (SFI). The base station may indicate the slot format by indicating the index of the table configured through UE-specific RRC signaling using SFI, and may indicate dynamically through DCI (Downlink Control Information) or statically or through RRC. It can also be ordered quasi-statically.

<NR Physical Resources>

In relation to a physical resource in NR, an antenna port, a resource grid, a resource element, a resource block, a bandwidth part, etc. are considered do.

An antenna port is defined such that a channel on which a symbol on an antenna port is carried can be inferred from a channel on which another symbol on the same antenna port is carried. When the large-scale property of a channel on which a symbol on one antenna port is carried can be inferred from a channel on which a symbol on another antenna port is carried, the two antenna ports are QC/QCL (quasi co-located or QC/QCL) It can be said that there is a quasi co-location) relationship. Here, the wide range characteristic includes one or more of delay spread, Doppler spread, frequency shift, average received power, and received timing.

3 is a diagram for explaining a resource grid supported by a radio access technology to which this embodiment can be applied.

Referring to FIG. 3 , in the resource grid, since NR supports a plurality of numerologies on the same carrier, a resource grid may exist according to each numerology. In addition, the resource grid may exist according to an antenna port, a subcarrier interval, and a transmission direction.

A resource block consists of 12 subcarriers, and is defined only in the frequency domain. In addition, a resource element is composed of one OFDM symbol and one subcarrier. Accordingly, as in FIG. 3 , the size of one resource block may vary according to the subcarrier interval. In addition, NR defines "Point A" serving as a common reference point for a resource block grid, a common resource block, a virtual resource block, and the like.

4 is a diagram for explaining a bandwidth part supported by a radio access technology to which the present embodiment can be applied.

In NR, unlike LTE in which the carrier bandwidth is fixed at 20Mhz, the maximum carrier bandwidth is set from 50Mhz to 400Mhz for each subcarrier interval. Therefore, it is not assumed that all terminals use all of these carrier bandwidths. Accordingly, in NR, as shown in FIG. 4, a bandwidth part (BWP) may be designated within the carrier bandwidth and used by the terminal. In addition, the bandwidth part is associated with one neurology and is composed of a subset of continuous common resource blocks, and may be dynamically activated according to time. Up to four bandwidth parts are configured in the terminal, respectively, in uplink and downlink, and data is transmitted/received using the activated bandwidth part at a given time.

In the case of a paired spectrum, the uplink and downlink bandwidth parts are set independently, and in the case of an unpaired spectrum, to prevent unnecessary frequency re-tunning between downlink and uplink operations For this purpose, the downlink and uplink bandwidth parts are set in pairs to share a center frequency.

<NR Initial Connection>

In NR, the terminal accesses the base station and performs a cell search and random access procedure in order to perform communication.

Cell search is a procedure in which the terminal synchronizes with the cell of the corresponding base station using a synchronization signal block (SSB) transmitted by the base station, obtains a physical layer cell ID, and obtains system information.

5 is a diagram exemplarily illustrating a synchronization signal block in a radio access technology to which the present embodiment can be applied.

Referring to FIG. 5, the SSB consists of a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) occupying 1 symbol and 127 subcarriers, respectively, and a PBCH spanning 3 OFDM symbols and 240 subcarriers.

The UE receives the SSB by monitoring the SSB in the time and frequency domains.

SSB can be transmitted up to 64 times in 5ms. A plurality of SSBs are transmitted using different transmission beams within 5 ms, and the UE performs detection on the assumption that SSBs are transmitted every 20 ms when viewed based on one specific beam used for transmission. The number of beams that can be used for SSB transmission within 5 ms time may increase as the frequency band increases. For example, up to 4 SSB beams can be transmitted in 3 GHz or less, and SSB can be transmitted using up to 8 different beams in a frequency band of 3 to 6 GHz and up to 64 different beams in a frequency band of 6 GHz or more.

Two SSBs are included in one slot, and the start symbol and the number of repetitions within the slot are determined according to the subcarrier interval as follows.

On the other hand, the SSB is not transmitted at the center frequency of the carrier bandwidth, unlike the SS of the conventional LTE. That is, the SSB may be transmitted in a place other than the center of the system band, and a plurality of SSBs may be transmitted in the frequency domain when wideband operation is supported. Accordingly, the UE monitors the SSB using a synchronization raster that is a candidate frequency location for monitoring the SSB. The carrier raster and synchronization raster, which are the center frequency location information of the channel for initial access, are newly defined in NR. Compared to the carrier raster, the synchronization raster has a wider frequency interval than that of the carrier raster. can

The UE may acquire the MIB through the PBCH of the SSB. MIB (Master Information Block) includes minimum information for the terminal to receive the remaining system information (RMSI, Remaining Minimum System Information) broadcast by the network. In addition, the PBCH includes information on the position of the first DM-RS symbol in the time domain, information for the UE to monitor SIB1 (eg, SIB1 neurology information, information related to SIB1 CORESET, search space information, PDCCH related parameter information, etc.), offset information between the common resource block and the SSB (the position of the absolute SSB in the carrier is transmitted through SIB1), and the like. Here, the SIB1 neurology information is equally applied to some messages used in the random access procedure for accessing the base station after the UE completes the cell search procedure. For example, the neurology information of SIB1 may be applied to at least one of messages 1 to 4 for the random access procedure.

The aforementioned RMSI may mean System Information Block 1 (SIB1), and SIB1 is periodically broadcast (eg, 160 ms) in the cell. SIB1 includes information necessary for the UE to perform an initial random access procedure, and is periodically transmitted through the PDSCH. In order for the UE to receive SIB1, it must receive neurology information used for SIB1 transmission and CORESET (Control Resource Set) information used for scheduling SIB1 through the PBCH. The UE checks scheduling information for SIB1 by using SI-RNTI in CORESET, and acquires SIB1 on PDSCH according to the scheduling information. SIBs other than SIB1 may be transmitted periodically or may be transmitted according to the request of the terminal.

6 is a diagram for explaining a random access procedure in a radio access technology to which this embodiment can be applied.

Referring to FIG. 6 , upon completion of cell search, the terminal transmits a random access channel preamble for random access to the base station. The random access channel preamble is transmitted through the PRACH. Specifically, the random access channel preamble is transmitted to the base station through a PRACH consisting of continuous radio resources in a periodically repeated specific slot. In general, when a UE initially accesses a cell, a contention-based random access procedure is performed, and when random access is performed for beam failure recovery (BFR), a contention-free random access procedure is performed.

The terminal receives a random access response to the transmitted random access channel preamble. The random access response may include a random access channel preamble identifier (ID), a UL grant (uplink radio resource), a temporary C-RNTI (Temporary Cell - Radio Network Temporary Identifier), and a Time Alignment Command (TAC). Since one random access response may include random access response information for one or more terminals, the random access channel preamble identifier may be included to inform which terminal the included UL Grant, temporary C-RNTI, and TAC are valid. . The random access channel preamble identifier may be an identifier for the random access channel preamble received by the base station. The TAC may be included as information for the UE to adjust uplink synchronization. The random access response may be indicated by a random access identifier on the PDCCH, that is, RA-RNTI (Random Access - Radio Network Temporary Identifier).

Upon receiving the valid random access response, the terminal processes information included in the random access response and performs scheduled transmission to the base station. For example, the UE applies the TAC and stores the temporary C-RNTI. In addition, data stored in the buffer of the terminal or newly generated data is transmitted to the base station by using the UL grant. In this case, information for identifying the terminal should be included.

Finally, the terminal receives a downlink message for contention resolution.

<NR CORESET>

The downlink control channel in NR is transmitted in a CORESET (Control Resource Set) having a length of 1 to 3 symbols, and transmits uplink/downlink scheduling information, SFI (Slot Format Index), and TPC (Transmit Power Control) information. .

As such, in NR, the concept of CORESET was introduced in order to secure the flexibility of the system. CORESET (Control Resource Set) means a time-frequency resource for a downlink control signal. The UE may decode the control channel candidates by using one or more search spaces in the CORESET time-frequency resource. Quasi CoLocation (QCL) assumptions for each CORESET are set, and this is used for the purpose of notifying the characteristics of the analog beam direction in addition to the delay spread, Doppler spread, Doppler shift, and average delay, which are characteristics assumed by the conventional QCL.

7 is a diagram for explaining CORESET.

Referring to FIG. 7 , CORESET may exist in various forms within a carrier bandwidth within one slot, and CORESET may consist of up to three OFDM symbols in the time domain. In addition, CORESET is defined as a multiple of 6 resource blocks up to the carrier bandwidth in the frequency domain.

The first CORESET is indicated through the MIB as part of the initial bandwidth part configuration to receive additional configuration information and system information from the network. After connection establishment with the base station, the terminal may receive and configure one or more pieces of CORESET information through RRC signaling.

In the present specification, frequencies, frames, subframes, resources, resource blocks, regions, bands, subbands, control channels, data channels, synchronization signals, various reference signals, various signals or various messages related to NR (New Radio) can be interpreted in various meanings used in the past or present or used in the future.

New Radio (NR)

Recently, NR conducted in 3GPP was designed to satisfy various QoS requirements required for each segmented and detailed service requirement (usage scenario) as well as an improved data rate compared to LTE. In particular, eMBB (enhancement Mobile BroadBand), mMTC (massive machine type communication), and URLLC (Ultra Reliable and Low Latency Communications) have been defined as representative service requirements (usage scenario) of NR, and each service requirement (usage scenario) requires As a method to satisfy , a flexible frame structure design compared to LTE/LTE-Advanced is required.

Frequency constituting an arbitrary NR system because each service requirement (usage scenario) has different requirements for data rates, latency, reliability, coverage, etc. A radio resource unit based on different numerology (eg, subcarrier spacing, subframe, TTI, etc.) as a method for efficiently satisfying the needs of each service requirement (usage scenario) through the band It is designed to efficiently multiplex the

As one method for this, TDM, FDM or TDM/FDM-based through one or a plurality of NR component carriers (s) for numerology with different subcarrier spacing values Discussion was made on a method of supporting by multiplexing to and supporting one or more time units in configuring a scheduling unit in a time domain. In this regard, in NR, a subframe is defined as a type of time domain structure, and reference numerology for defining the subframe duration is used. As a result, it was decided to define a single subframe duration composed of 14 OFDM symbols of the same 15 kHz Sub-Carrier Spacing (SCS)-based normal CP overhead as LTE. Accordingly, in NR, a subframe has a duration of 1 ms. However, unlike LTE, the NR subframe is an absolute reference time duration, and a slot and a mini-slot as a time unit that is the basis of actual up/downlink data scheduling. ) can be defined. In this case, the number of OFDM symbols constituting the corresponding slot, the y value, is determined to have a value of y=14 regardless of the SCS value in the case of a normal CP.

Accordingly, any slot consists of 14 symbols, and according to the transmission direction of the slot, all symbols are used for downlink transmission (DL transmission), or all symbols are used for uplink transmission (UL). transmission), or may be used in the form of a downlink portion (DL portion) + a gap + an uplink portion (UL portion).

In addition, a mini-slot composed of a smaller number of symbols than the slot is defined in an arbitrary numerology (or SCS), and based on this, a short time domain scheduling interval for uplink/downlink data transmission/reception (time-domain) is defined. scheduling interval) may be set, or a long time-domain scheduling interval for uplink/downlink data transmission/reception may be configured through slot aggregation.

In particular, in the case of transmission and reception of latency critical data such as URLLC, 1ms (14 symbols) defined in a numerology-based frame structure with a small SCS value such as 15kHz When scheduling is performed in units of slots, it may be difficult to satisfy the latency requirement. For this purpose, a mini-slot composed of fewer OFDM symbols than the corresponding slot is defined, and based on this, it is critical to the same latency as the URLLC. It can be defined so that scheduling of (latency critical) data is performed.

Alternatively, as described above, by multiplexing and supporting numerology having different SCS values in one NR carrier in the TDM and/or FDM scheme, each numerology A method of scheduling data according to a latency requirement based on a defined slot (or mini-slot) length is also being considered. For example, when the SCS is 60 kHz as shown in FIG. 8 below, since the symbol length is reduced by about 1/4 compared to the case of SCS 15 kHz, if one slot is configured with 14 OFDM symbols, the corresponding 15 kHz-based The slot length becomes 1 ms, whereas the slot length based on 60 kHz is reduced to about 0.25 ms.

As such, in NR, by defining different SCS or different TTI lengths, a discussion is ongoing on a method of satisfying the requirements of URLLC and eMBB, respectively.

Wider bandwidth operations

In the case of the existing LTE system, a scalable bandwidth operation for an arbitrary LTE CC (Component Carrier) was supported. That is, according to a frequency distribution scenario (deployment scenario), any LTE operator was able to configure a bandwidth of at least 1.4 MHz to a maximum of 20 MHz in configuring one LTE CC, and a normal LTE terminal is one LTE For CC, the transmit/receive capability of 20 MHz bandwidth was supported.

However, in the case of NR, the design is made to enable support for NR terminals having different transmission/reception bandwidth capabilities through one wideband NR CC. By configuring one or more bandwidth parts (BWP, bandwidth part(s)) composed of a segmented bandwidth for an arbitrary NR CC, flexible (bandwidth part configuration) and activation (activation) different for each terminal It is required to support a wider bandwidth operation that is flexible.

Specifically, in NR, one or more bandwidth parts may be configured through one serving cell configured from the viewpoint of the terminal, and the terminal may configure one downlink bandwidth part in the corresponding serving cell (serving cell). DL bandwidth part) and one uplink bandwidth part (UL bandwidth part) are activated and defined to be used for uplink/downlink data transmission/reception. In addition, when a plurality of serving cells are configured in the corresponding terminal, that is, one downlink bandwidth part and/or uplink bandwidth part is activated for each serving cell even for a terminal to which CA is applied (activation) Thus, it is defined to be used for uplink/downlink data transmission/reception using radio resources of the corresponding serving cell.

Specifically, an initial bandwidth part for an initial access procedure of a terminal is defined in an arbitrary serving cell, and one or more terminal specific (UE) through dedicated RRC signaling for each terminal -specific) A bandwidth part(s) is configured, and a default bandwidth part for a fallback operation may be defined for each terminal.

However, a plurality of downlink and/or uplink bandwidth parts are activated and used at the same time according to the configuration of the terminal's capability and bandwidth part(s) in an arbitrary serving cell. However, in NR rel-15, it is defined to activate and use only one downlink bandwidth part (DL bandwidth part) and an uplink bandwidth part (UL bandwidth part) at any time in any terminal. .

random access procedure

Random access is a procedure used by the terminal to synchronize uplink time with the base station or to be allocated radio resources.

The UE performs a random access procedure in the following cases.

- In case of initial connection because there is no RRC connection with the base station

- When trying to recover from wireless connection failure or handover failure

- When the terminal accesses the target cell for the first time during the handover process

- If the uplink time synchronization is not aligned or to request a radio resource (UL grant)

- When requested by the base station

Such a random access procedure is divided into a contention based random access procedure and a non-contention based or contention free random access procedure. The distinction between the two methods is determined according to whether the UE directly selects a preamble used in the random access process or the base station selects the preamble.

In a non-contention based (contention free) random access process, the terminal uses the preamble allocated only to itself by the base station. That is, the base station allocates a preamble for each terminal to use for non-contention-based random access. Since the preamble allocated to each terminal cannot be used by other terminals, a collision does not occur.

Thereafter, the terminal transmits the random access channel preamble to the base station by using the allocated preamble when the above-described random access procedure is performed. When the base station receives the random access channel preamble, the base station transmits a random access response to the corresponding terminal. Upon receiving the random access response, the UE synchronizes the uplink time using a Timing Advance Command (TAC) included in the random access response, and prepares to transmit uplink data to the corresponding resource according to the UL grant. As a result, the random access procedure is terminated.

In the contention-based random access procedure, the UE selects and transmits a random preamble among available preambles by itself. In this case, since the terminal arbitrarily selects the random access channel preamble, there is a possibility of being selected and used simultaneously by several terminals. Therefore, when the base station receives a random access channel preamble, it cannot know from which terminal the corresponding random access channel preamble is transmitted. Therefore, unlike the non-contention-based random access procedure, an additional process for allowing only one UE to be selected is required. Hereinafter, a contention-based random access procedure will be described in the order of FIG. 4 .

One. First, the terminal arbitrarily selects one random access channel preamble from a set of random access channel preambles set through the received system information, and selects and transmits a PRACH resource capable of transmitting the selected random access channel preamble. PRACH resource configuration is provided through system information. The PRACH resource can know which subframe is allocated at which period and through the PRACH configuration index of the system information block 2 (system information block2).

2. The base station transmits a response message for one of the received random access channel preambles. The random access response is delivered within the random access response window delivered through system information. The random access response message may be composed of a random access channel preamble ID, an uplink radio resource (UL grant), a temporary C-RNTI (Temporary C-RNTI), an uplink time synchronization correction value (Time Alignment Command), and the like.

When the terminal receives a random access response corresponding to the random access channel preamble transmitted by the terminal, it sets content included in the random access response. For example, the UE applies the TAC and sets the temporary C-RNTI included in the random access response message as its own temporary C-RNTI. Then, it prepares to transmit a message through the received uplink radio resource. At this time, other terminals that have transmitted the same random access channel preamble through the same PRACH resource also receive the random access response, so that the above-described configuration is applied and Msg3 is transmitted together.

3. The terminal transmits Msg3 through the received radio resource as the received temporary C-RNTI. Msg3 includes UE-specific information such as UE-Identity.

4. The base station prepares a response message for one Msg3 that is received from the terminal and successfully decoded. Msg4 is configured including the UE's unique identifier (contention resolution ID=ue-Identity) included in Msg3 and transmitted as a temporary C-RNTI (S440).

5. Upon receiving the response message (Msg4), the terminal compares the unique identifier included in Msg4 with its own identifier and, if the same, considers it a response of Msg3 that it has transmitted and transmits an ACK to the base station. If the unique identifier included in the received Msg4 is not the same as its own unique identifier, the terminal determines that the random access process has failed, and starts the random access process again from the beginning.

Through the above process, it is possible to avoid collision of multiple terminals that transmit the same random access channel preamble through the same PRACH resource in the contention-based random access process.

Random Access Channel Preamble

A random access channel preamble used in the random access procedure will be briefly described.

A total of 64 random access channel preambles can be divided. It is largely divided into a non-dedicated random access channel preamble (Non-dedicated RA preamble) and a dedicated random access channel preamble (Dedicated RA preamble). The non-dedicated random access channel preamble is a set of preambles that can be used in a contention-based random access procedure. In addition, the dedicated random access channel preamble is a set of preambles used in a non-contention-based random access procedure. The non-dedicated random access channel preambles are further divided into Group A and Group B. Group A and Group B are divided according to the size and path loss of message 3 (Msg3) in the random access procedure. The base station divides in advance the type and number of preambles that the terminal can use according to the situation through the System Information Block 2 (SIB2) and allocates it.

Random Access Response

The terminal that has transmitted the random access channel preamble generates an RA-RNTI according to the PRACH resource that has transmitted the random access channel preamble. The UE monitors the reception of the random access response for a preset random access response window (RAR window) time through SIB2 after three subframes from the subframe in which the random access channel preamble is transmitted. In this case, the UE monitors the reception of the random access response using the above-described RA-RNTI. If the terminal receives the random access response message within the response window, it adjusts its uplink time synchronization according to the TAC included in the random access response message, sets the temporary C-RNTI to its RNTI, and sets the temporary C -Using RNTI, prepares to transmit the above-described Msg3 according to the uplink grant.

In the conventional 3GPP NR, as described above, the following process is performed for base station access.

As a step 1, when the base station performs periodic transmission of the SSB, in step 2, the UE performs PRACH location detection through detection of the transmitted SSB and SIB acquisition, and transmits a random access channel preamble to the corresponding location do. In step 3, the base station transmits Msg2, which is a response corresponding to the received RACH preamble, and transmits timing information and PUSCH scheduling information through the corresponding message. In step 4, the terminal transmits Msg3 user information through the resource indicated through the corresponding response, and in step 5, the base station releases terminal information acquisition and contention through the corresponding Msg3, and starts communication.

Here, steps 2, 3, 4, and 5 are well-known 4-step RACH procedures, and a 2-step RACH procedure that combines steps 2 and 4 and steps 3 and 5 has been defined and standardized.

The reach of the SSB and RACH preamble signals in the base station access step is very wide compared to the actual data coverage. This is to enable a user near a cell or out of coverage to confirm the existence of a cell, obtain channel quality, and perform an appropriate handover. However, in order to successfully transmit the actual Msg2, etc., the UE must be located much closer than the SSB and Preamble signal reach.

The present disclosure provides a method for successfully transmitting subsequent messages even in a channel environment where messages of Msg2 or less cannot reach for coverage extension in an NR system. Specifically, a method for operating a RACH preamble for classifying a coverage extension support terminal, a transmission method for a coverage extension support terminal, and a base station transmission method for a coverage extension support terminal are provided.

Hereinafter, a method of performing a random access procedure for coverage extension will be specifically described with reference to related drawings.

10 is a diagram illustrating a procedure in which a terminal performs a random access procedure for coverage extension according to an embodiment.

Referring to FIG. 10 , the UE may transmit a random access channel preamble for repeated transmission of Msg3 through a Physical Random Access Channel (PRACH) (S1000).

The terminal detects the SSB transmitted from the base station in order to access the base station and performs PRACH location detection through SIB acquisition. Based on this, the terminal transmits a random access channel preamble (RACH Preamble) to the base station.

According to an example, when coverage extension is supported, the terminal may transmit a separate RACH preamble for repeated transmission of Msg3 to the base station. That is, a new RACH preamble that is distinct from the RACH preamble transmitted in the general case where repeated transmission of Msg3 is not requested may be configured. That is, when the RACH preamble is transmitted in a new method different from the general case, the base station can confirm that the terminal that has transmitted the RACH preamble is a terminal that supports coverage extension.

In order to transmit the RACH preamble for repeated transmission of Msg3, a separate PRACH resource through which only the coverage extension supporting terminal can transmit the corresponding RACH preamble may be configured in advance.

As an example, a separate PRACH resource may be separately defined on a time/frequency resource. For example, PRACH opportunities in a slot in which a RACH preamble for repeated transmission of Msg3 may be transmitted may be preconfigured to be distinguished from PRACH opportunities in which a general RACH preamble may be transmitted. Such configuration information may be included in system information and transmitted from the base station.

In this case, for example, separately configured PRACH opportunities may be configured by shifting general PRACH opportunities to a predetermined value in a frequency domain or a time domain. However, this is an example, and the present invention is not limited thereto, and separately configured PRACH opportunities may be configured irrespective of the configuration of general PRACH opportunities.

Based on the corresponding configuration information, the UE may transmit a RACH preamble for repeated transmission of Msg3 based on separately configured PRACH opportunities. When the RACH preamble is received from among the PRACH opportunities configured separately, the base station may determine that the corresponding terminal has requested repeated transmission of Msg3 for coverage extension. In this case, the RACH preamble may be configured in the same way as the RACH preamble in the general case.

Alternatively, according to another example, the UE may determine the RACH preamble in the form of a preamble sequence used only by the UE supporting the coverage extension. That is, the RACH preamble for repeated transmission of Msg3 may be configured based on a sequence different from a sequence in a general case in which repeated transmission of Msg3 is not performed.

Based on the configuration information of the corresponding RACH preamble, the UE may configure and transmit the RACH preamble for repeated transmission of Msg3 based on a separate sequence. When a RACH preamble composed of a separate sequence is received among PRACH opportunities, the base station may determine that the corresponding terminal has requested repeated transmission of Msg3 for coverage extension. In this case, the PRACH opportunities may be configured the same as the PRACH opportunities in the general case.

Or, according to another example, the random access preamble for repeated transmission of Msg3 is configured based on a different sequence distinguished from the sequence in the general case of not repeatedly transmitting Msg3, and transmitted based on separately configured PRACH opportunities can be That is, in order to request repeated transmission of Msg3, the UE may configure a RACH preamble based on a separate sequence and transmit it based on separately configured PRACH opportunities.

According to an example, the UE may determine whether to transmit the RACH preamble for repeated transmission of Msg3 based on Reference Signal Received Power (RSRP) of the received synchronization signal. That is, in the case where the channel condition is not good, such as when the RSRP value of the synchronization signal received from the base station is smaller than a predetermined threshold, the terminal determines to transmit the RACH preamble for repeated transmission of Msg3 in order to extend the coverage. can

Referring back to FIG. 10, the UE receives a random access response (RAR) including uplink scheduling information for repeated transmission of Msg3 (S1010), and repeatedly transmits Msg3 based on the uplink scheduling information. It can be (S1020).

When the RACH preamble for repeated transmission of Msg3 is received, the base station may determine whether to allocate resources for repeated transmission of Msg3 to the terminal. The base station may transmit a random access response including uplink resource information to be used for repeated transmission so that the terminal can repeatedly transmit Msg3.

According to an example, when allocating a resource for repeated transmission of Msg3, the base station may determine the number of repetitions of Msg3. The base station may indicate the number of repetitions of Msg3 through downlink control information. In this case, according to an example, the corresponding downlink control information may be configured in DCI format 0_0 having CRC scrambled with TC (Temporary Cell)-RNTI.

According to an example, the base station may determine a redundancy version (RV) related to repeated Msg3 transmission. Msg3 may be configured to use RV 0 for the first iteration of the initial transmission. The base station may dynamically indicate the RV ID through DCI 0_0 with CRC scrambled by TC-RNTI for the first repetition of Msg3 retransmission.

The UE may repeatedly transmit Msg3 using a corresponding resource according to an uplink grant included in the random access response.

According to this, it is possible to provide a specific method and apparatus capable of extending coverage by repeatedly transmitting Msg3 in a random access procedure in NR.

11 is a diagram illustrating a procedure in which a base station performs a random access procedure for coverage extension according to an embodiment.

Referring to FIG. 11 , the base station may receive a random access channel preamble for repeated transmission of Msg3 through a physical random access channel (PRACH) (S1100).

The base station transmits a synchronization signal and system information. The terminal detects the SSB transmitted from the base station in order to access the base station and performs PRACH location detection through SIB acquisition. The base station receives a random access channel preamble (RACH Preamble) transmitted by the terminal based on the corresponding information.

According to an example, the base station may preconfigure configuration information for transmitting a separate RACH preamble for repeated transmission of Msg3 to the terminal in which the coverage extension is supported, and transmit the configuration information to the terminal. That is, a new RACH preamble that is distinct from the RACH preamble transmitted in the general case where repeated transmission of Msg3 is not requested may be configured. That is, when the RACH preamble is transmitted from the terminal in a new method different from the general case, the base station can confirm that the terminal that transmitted the RACH preamble is a terminal that supports coverage extension.

In order to transmit the RACH preamble for repeated transmission of Msg3, a separate PRACH resource through which only the coverage extension supporting terminal can transmit the corresponding RACH preamble may be configured in advance.

As an example, a separate PRACH resource may be separately defined on a time/frequency resource. For example, PRACH opportunities in a slot in which a RACH preamble for repeated transmission of Msg3 may be transmitted may be preconfigured to be distinguished from PRACH opportunities in which a general RACH preamble may be transmitted. The base station may transmit such configuration information by including it in system information.

In this case, for example, separately configured PRACH opportunities may be configured by shifting general PRACH opportunities to a predetermined value in a frequency domain or a time domain. However, this is an example, and the present invention is not limited thereto, and separately configured PRACH opportunities may be configured irrespective of the configuration of general PRACH opportunities.

Based on the corresponding configuration information, the base station may receive a RACH preamble for repeated transmission of Msg3 based on separately configured PRACH opportunities. When the RACH preamble is received from among the PRACH opportunities configured separately, the base station may determine that the corresponding terminal has requested repeated transmission of Msg3 for coverage extension. In this case, the RACH preamble may be configured in the same way as the RACH preamble in the general case.

Alternatively, according to another example, the UE may determine the RACH preamble in the form of a preamble sequence used only by the UE supporting the coverage extension. That is, the RACH preamble for repeated transmission of Msg3 may be configured based on a sequence different from a sequence in a general case in which repeated transmission of Msg3 is not performed.

Based on the configuration information of the RACH preamble, the base station may receive the RACH preamble for repeated transmission of Msg3 configured based on a separate sequence. When a RACH preamble composed of a separate sequence is received among PRACH opportunities, the base station may determine that the corresponding terminal has requested repeated transmission of Msg3 for coverage extension. In this case, the PRACH opportunities may be configured the same as the PRACH opportunities in the general case.

Or, according to another example, the random access preamble for repeated transmission of Msg3 is configured based on a different sequence differentiated from the sequence in the general case of not repeatedly transmitting Msg3, and received based on separately configured PRACH opportunities can be That is, in order to request repeated transmission of Msg3, the UE may configure a RACH preamble based on a separate sequence and transmit it based on separately configured PRACH opportunities.

According to an example, the UE may determine whether to transmit the RACH preamble for repeated transmission of Msg3 based on Reference Signal Received Power (RSRP) of the received synchronization signal. That is, in the case where the channel condition is not good, such as when the RSRP value of the synchronization signal received from the base station is smaller than a predetermined threshold, the terminal determines to transmit the RACH preamble for repeated transmission of Msg3 in order to extend the coverage. can

Referring back to FIG. 11 , the base station transmits a random access response (RAR) including uplink scheduling information for repeated transmission of Msg3 (S1110), and repeatedly receives Msg3 based on the uplink scheduling information. It can be done (S1120).

When the RACH preamble for repeated transmission of Msg3 is received, the base station may determine whether to allocate resources for repeated transmission of Msg3 to the terminal. The base station may transmit a random access response including uplink resource information to be used for repeated transmission so that the terminal can repeatedly transmit Msg3.

According to an example, when allocating a resource for repeated transmission of Msg3, the base station may determine the number of repetitions of Msg3. The base station may indicate the number of repetitions of Msg3 through downlink control information. In this case, according to an example, the corresponding downlink control information may be configured in DCI format 0_0 having CRC scrambled with TC (Temporary Cell)-RNTI.

According to an example, the base station may determine a redundancy version (RV) related to repeated Msg3 transmission. Msg3 may be configured to use RV 0 for the first iteration of the initial transmission. The base station may dynamically indicate the RV ID through DCI 0_0 with CRC scrambled by TC-RNTI for the first repetition of Msg3 retransmission.

The UE may repeatedly transmit Msg3 using a corresponding resource according to an uplink grant included in the random access response.

According to this, it is possible to provide a specific method and apparatus capable of extending coverage by repeatedly transmitting Msg3 in a random access procedure in NR.

Hereinafter, each embodiment related to a method of performing a random access procedure for coverage extension in NR will be described in detail with reference to related drawings. The embodiments described below may be applied individually or in any combination.

In the present disclosure, for coverage extension in the NR system, (1) a RACH preamble operation method for distinguishing a coverage extension support terminal , (2) a transmission method of a coverage extension support terminal , and (3) transmission of a base station for a coverage extension support terminal method can be provided.

Embodiment 1. RACH preamble operation method for classification of coverage extension support terminals

This embodiment is a method of operating the RACH preamble so that the base station receiving the random access channel preamble signal can know that the transmitting terminal is a coverage extension support terminal. This may be divided into a transmission resource through which the RACH preamble is transmitted or a transmission method of the RACH preamble. Specifically, the following methods may be used.

① How to define a separate PRACH resource for a coverage extension support terminal

The corresponding method is to configure in advance a separate PRACH resource through which only the coverage extension supporting terminal can transmit the RACH preamble. As an example, a separate PRACH resource may be separately defined on a time/frequency resource. Alternatively, the RACH preamble may be determined in the form of a preamble sequence used only by a coverage extension supporting terminal.

② How the coverage extension supporting terminal introduces a separate PRACH preamble transmission method

This method is a method in which the coverage extension supporting terminal transmits the PRACH preamble in a different form from that of other terminals. For example, the coverage extension support terminal may transmit a plurality of identical or regularly changing preamble sequences with a predetermined period. The base station can detect this pattern when receiving the PRACH preamble, and determine that the corresponding terminal is a coverage extension support terminal.

Embodiment 2. Transmission method of coverage extension support terminal

This embodiment is a method that enables successful control/data message transmission when the coverage extension support terminal is outside the conventional coverage. This is done by repeated transmission of the same or equivalent signal, and the corresponding repetition pattern must be agreed in advance. In this regard, there are a method of repeatedly transmitting to another resource in the time axis and a method of repeatedly transmitting to another resource in the frequency axis.

① How to repeatedly transmit to other resources in the time axis

In this method, when the coverage extension support terminal performs all transmissions, the same or equivalent signal is transmitted again in the next slot or a slot spaced apart by a preset amount. To this end, the base station may determine the number of repetitions or the slot interval depending on the PRACH preamble, or may set it through RRC in advance, or may designate the number of repetitions in each scheduling DCI. When set in DCI, this may be set as a separate field or may be included as a parameter in a Time Domain Resource Allocation (TDRA) table defined for a corresponding UE. This DCI may be scrambled with a newly introduced RNTI so that only a coverage extension user can receive it.

② Repeated transmission to other resources on the frequency axis

In this method, when the coverage extension support terminal performs all transmissions, the same or equivalent signals are repeatedly transmitted in different bands. To this end, the base station may determine the number of repetitions depending on the PRACH preamble, or may be set in advance through RRC or the like, or set at every DCI. In addition, a frequency band allocated during DCI scheduling may be allocated in consideration of both transmissions. That is, the UE divides the allocated resources using a certain rule, and may transmit the same or equivalent signals to each resource by overlapping them. This DCI may likewise be scrambled with a newly introduced RNTI so that only a coverage extension user can receive it.

Embodiment 3. Transmission method of a base station for a coverage extension support terminal

This embodiment is a method that enables successful control/data message reception when the coverage extension support terminal is outside the conventional coverage. This method also consists of repeated transmission of the same or equivalent signal as in terminal transmission, and the corresponding repetition pattern must be agreed in advance. Broadly, there are a method of repeatedly transmitting to other resources in the time axis and a method of repeatedly transmitting to other resources in the frequency axis. As for the specific methods, the same types of methods as ① and ② of the above-described embodiment 2 may be used.

The methods provided in the present disclosure may be applied independently, or may be operated in combination in any form. In addition, in the case of a new term, an arbitrary name that is easy to understand the meaning of the term used in the present disclosure is used, and the invention of the present disclosure can be applied even when other terms having the same meaning are actually used.

Hereinafter, configurations of a terminal and a base station capable of performing some or all of the embodiments described with reference to FIGS. 1 to 11 will be described with reference to the drawings.

12 is a diagram showing the configuration of a terminal 1200 according to another embodiment.

Referring to FIG. 12 , the terminal 1200 according to another embodiment includes a controller 1210 , a transmitter 1220 , and a receiver 1230 .

The controller 1210 controls the overall operation of the terminal 1200 according to a method for performing a random access procedure for a coverage extension by a terminal necessary for carrying out the above-described present invention. The transmitter 1220 transmits uplink control information, data, and messages to the base station through a corresponding channel, and transmits sidelink control information, data, and messages to other terminals through the corresponding channel. The receiving unit 1230 receives downlink control information, data, and messages from the base station through a corresponding channel, and receives sidelink control information, data, and messages from other terminals through the corresponding channel.

The transmitter 1220 may transmit a random access channel preamble for repeated transmission of Msg3 through a Physical Random Access Channel (PRACH).

The controller 1210 and the receiver 1230 detect the SSB transmitted from the base station to access the base station, and perform PRACH location detection through SIB acquisition. Based on this, the transmitter 1220 transmits a random access channel preamble (RACH Preamble) to the base station.

According to an example, when coverage extension is supported, the transmitter 1220 may transmit a separate RACH preamble for repeated transmission of Msg3 to the base station. That is, a new RACH preamble that is distinct from the RACH preamble transmitted in the general case where repeated transmission of Msg3 is not requested may be configured. That is, when the RACH preamble is transmitted in a new method different from the general case, the base station can confirm that the terminal that has transmitted the RACH preamble is a terminal that supports coverage extension.

In order to transmit the RACH preamble for repeated transmission of Msg3, a separate PRACH resource through which only the coverage extension supporting terminal can transmit the corresponding RACH preamble may be configured in advance.

As an example, a separate PRACH resource may be separately defined on a time/frequency resource. For example, PRACH opportunities in a slot in which a RACH preamble for repeated transmission of Msg3 may be transmitted may be preconfigured to be distinguished from PRACH opportunities in which a general RACH preamble may be transmitted. Such configuration information may be included in system information and transmitted from the base station.

Based on the corresponding configuration information, the transmitter 1220 may transmit a RACH preamble for repeated transmission of Msg3 based on separately configured PRACH opportunities. When the RACH preamble is received from among the PRACH opportunities configured separately, the base station may determine that the corresponding terminal has requested repeated transmission of Msg3 for coverage extension. In this case, the RACH preamble may be configured in the same way as the RACH preamble in the general case.

Alternatively, according to another example, the controller 1210 may determine the RACH preamble in the form of a preamble sequence used only by the coverage extension support terminal. That is, the RACH preamble for repeated transmission of Msg3 may be configured based on a sequence different from a sequence in a general case in which repeated transmission of Msg3 is not performed.

Based on the configuration information of the RACH preamble, the transmitter 1220 may configure and transmit the RACH preamble for repeated transmission of Msg3 based on a separate sequence. When a RACH preamble composed of a separate sequence is received among PRACH opportunities, the base station may determine that the corresponding terminal has requested repeated transmission of Msg3 for coverage extension. In this case, the PRACH opportunities may be configured the same as the PRACH opportunities in the general case.

Or, according to another example, the random access preamble for repeated transmission of Msg3 is configured based on a different sequence distinguished from the sequence in the general case of not repeatedly transmitting Msg3, and transmitted based on separately configured PRACH opportunities can be

According to an example, the controller 1210 may determine whether to transmit the RACH preamble for repeated transmission of Msg3 based on Reference Signal Received Power (RSRP) of the received synchronization signal. That is, in the case where the channel condition is not good, such as when the RSRP value of the synchronization signal received from the base station is smaller than a predetermined threshold, the controller 1210 performs a RACH preamble for repeated transmission of Msg3 in order to extend the coverage. You can decide to send it.

The receiver 1230 may receive a random access response (RAR) including uplink scheduling information for repeated transmission of Msg3. Also, the transmitter 1220 may repeatedly transmit Msg3 based on uplink scheduling information.

When the RACH preamble for repeated transmission of Msg3 is received, the base station may determine whether to allocate resources for repeated transmission of Msg3 to the terminal. The base station may transmit a random access response including uplink resource information to be used for repeated transmission so that the terminal can repeatedly transmit Msg3.

The transmitter 1220 may repeatedly transmit Msg3 using a corresponding resource according to an uplink grant included in the random access response.

According to this, it is possible to provide a specific method and apparatus capable of extending coverage by repeatedly transmitting Msg3 in a random access procedure in NR.

13 is a diagram showing the configuration of a base station 1300 according to another embodiment.

Referring to FIG. 13 , a base station 1300 according to another embodiment includes a controller 1310 , a transmitter 1320 , and a receiver 1330 .

The controller 1310 controls the overall operation of the base station 1300 according to a method for performing a random access procedure for coverage extension by a base station necessary for carrying out the above-described present invention. The transmitter 1320 and the receiver 1330 are used to transmit/receive signals, messages, and data necessary for carrying out the present invention to and from the terminal.

The receiver 1330 may receive a random access channel preamble for repeated transmission of Msg3 through a Physical Random Access Channel (PRACH).

The transmitter 1320 transmits a synchronization signal and system information. The terminal detects the SSB transmitted from the base station in order to access the base station and performs PRACH location detection through SIB acquisition. The receiver 1330 receives a random access channel preamble (RACH Preamble) transmitted by the terminal based on the corresponding information.

According to an example, the transmitter 1320 may preconfigure configuration information for transmitting a separate RACH preamble for repeated transmission of Msg3 to a terminal supporting coverage extension and transmit it to the terminal. That is, a new RACH preamble that is distinct from the RACH preamble transmitted in the general case where repeated transmission of Msg3 is not requested may be configured. That is, when the RACH preamble is transmitted from the terminal in a new method different from the general case, the controller 1310 can confirm that the terminal that has transmitted the RACH preamble is a terminal that supports coverage extension.

In order to transmit the RACH preamble for repeated transmission of Msg3, a separate PRACH resource through which only the coverage extension supporting terminal can transmit the corresponding RACH preamble may be configured in advance.

As an example, a separate PRACH resource may be separately defined on a time/frequency resource. For example, PRACH opportunities in a slot in which a RACH preamble for repeated transmission of Msg3 may be transmitted may be preconfigured to be distinguished from PRACH opportunities in which a general RACH preamble may be transmitted. The transmitter 1320 may transmit the configuration information by including the configuration information in the system information.

Based on the corresponding configuration information, the receiver 1330 may receive the RACH preamble for repeated transmission of Msg3 based on separately configured PRACH opportunities. When the RACH preamble is received from among the PRACH opportunities configured separately, the controller 1310 may determine that the corresponding terminal has requested repeated transmission of Msg3 for coverage extension. In this case, the RACH preamble may be configured in the same way as the RACH preamble in the general case.

Alternatively, according to another example, the UE may determine the RACH preamble in the form of a preamble sequence used only by the UE supporting the coverage extension. That is, the RACH preamble for repeated transmission of Msg3 may be configured based on a sequence different from a sequence in a general case in which repeated transmission of Msg3 is not performed.

Based on the configuration information of the RACH preamble, the receiver 1330 may receive the RACH preamble for repeated transmission of Msg3 configured based on a separate sequence. When a RACH preamble composed of a separate sequence is received among PRACH opportunities, the controller 1310 may determine that the corresponding terminal has requested repeated transmission of Msg3 for coverage extension. In this case, the PRACH opportunities may be configured the same as the PRACH opportunities in the general case.

Or, according to another example, the random access preamble for repeated transmission of Msg3 is configured based on a different sequence differentiated from the sequence in the general case of not repeatedly transmitting Msg3, and received based on separately configured PRACH opportunities can be

According to an example, the UE may determine whether to transmit the RACH preamble for repeated transmission of Msg3 based on Reference Signal Received Power (RSRP) of the received synchronization signal. That is, in the case where the channel condition is not good, such as when the RSRP value of the synchronization signal received from the base station is smaller than a predetermined threshold, the terminal determines to transmit the RACH preamble for repeated transmission of Msg3 in order to extend the coverage. can

The transmitter 1320 may transmit a random access response (RAR) including uplink scheduling information for repeated transmission of Msg3. Also, the receiver 1330 may repeatedly receive Msg3 based on uplink scheduling information.

When the RACH preamble for repeated transmission of Msg3 is received, the controller 1310 may determine whether to allocate resources for repeated transmission of Msg3 to the UE. The transmitter 1320 may transmit a random access response including uplink resource information to be used for repeated transmission so that the terminal can repeatedly transmit Msg3.

The UE may repeatedly transmit Msg3 using a corresponding resource according to an uplink grant included in the random access response.

According to this, it is possible to provide a specific method and apparatus capable of extending coverage by repeatedly transmitting Msg3 in a random access procedure in NR.

The above-described embodiments may be supported by standard documents disclosed in at least one of IEEE 802, 3GPP and 3GPP2, which are wireless access systems. That is, steps, configurations, and parts not described in order to clearly reveal the present technical idea among the present embodiments may be supported by the above-described standard documents. In addition, all terms disclosed in this specification can be described by the standard documents disclosed above.

The above-described embodiments may be implemented through various means. For example, the present embodiments may be implemented by hardware, firmware, software, or a combination thereof.

In the case of implementation by hardware, the method according to the present embodiments may include one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), FPGAs (Field Programmable Gate Arrays), may be implemented by a processor, a controller, a microcontroller or a microprocessor.

In the case of implementation by firmware or software, the method according to the present embodiments may be implemented in the form of an apparatus, procedure, or function that performs the functions or operations described above. The software code may be stored in the memory unit and driven by the processor. The memory unit may be located inside or outside the processor, and may transmit/receive data to and from the processor by various well-known means.

Also, as described above, terms such as "system", "processor", "controller", "component", "module", "interface", "model", or "unit" generally refer to computer-related entities hardware, hardware and software. may mean a combination of, software, or running software. For example, the aforementioned component may be, but is not limited to, a process run by a processor, a processor, a controller, a controlling processor, an object, a thread of execution, a program, and/or a computer. For example, both an application running on a controller or processor and a controller or processor can be a component. One or more components may reside within a process and/or thread of execution, and the components may be located on one device (eg, a system, computing device, etc.) or distributed across two or more devices.

The above description is merely illustrative of the technical spirit of the present disclosure, and various modifications and variations will be possible without departing from the essential characteristics of the present disclosure by those skilled in the art to which the present disclosure pertains. In addition, the present embodiments are not intended to limit the technical spirit of the present disclosure, but rather to explain, so the scope of the present technical spirit is not limited by these embodiments. The protection scope of the present disclosure should be construed by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present disclosure.

Claims (20)

In a method for a terminal to perform a random access procedure for coverage extension,
Transmitting a random access channel preamble (RACH Preamble) for repeated transmission of Msg3 through a Physical Random Access Channel (PRACH);
receiving a random access response (RAR) including uplink scheduling information for repeated transmission of the Msg3; and
and repeatedly transmitting the Msg3 based on the uplink scheduling information. The method of claim 1,
The random access channel preamble for repeated transmission of Msg3 is,
A method of transmitting based on a PRACH opportunity configured separately from a PRACH opportunity when the Msg3 is not repeatedly transmitted. The method of claim 1,
The random access channel preamble for repeated transmission of Msg3 is,
A method configured based on a different sequence distinguished from a sequence in the case where the Msg3 is not repeatedly transmitted. The method of claim 1,
The random access channel preamble for repeated transmission of Msg3 is,
It is configured based on a different sequence that is distinguished from the sequence when the Msg3 is not repeatedly transmitted, and is transmitted based on a PRACH opportunity configured separately from the PRACH opportunity when the Msg3 is not repeatedly transmitted. The method of claim 1,
The random access channel preamble for repeated transmission of Msg3 is,
A method for determining whether to transmit based on Reference Signal Received Power (RSRP) of the received synchronization signal. A method for a base station to perform a random access procedure for coverage extension,
Receiving a random access channel preamble for repeated transmission of Msg3 (RACH Preamble) through a physical random access channel (PRACH);
transmitting a random access response (RAR) including uplink scheduling information for repeated transmission of the Msg3; and
and repeatedly receiving the Msg3 based on the uplink scheduling information. 7. The method of claim 6,
The random access channel preamble for repeated transmission of Msg3 is,
A method of receiving based on a PRACH opportunity configured separately from a PRACH opportunity when the Msg3 is not repeatedly transmitted. 7. The method of claim 6,
The random access channel preamble for repeated transmission of Msg3 is,
A method configured based on a different sequence distinguished from a sequence in the case where the Msg3 is not repeatedly transmitted. 7. The method of claim 6,
The random access channel preamble for repeated transmission of Msg3 is,
It is configured based on a different sequence differentiated from the sequence in the case of not repeatedly transmitting the Msg3, and is received based on a PRACH opportunity configured separately from the PRACH opportunity in the case in which the Msg3 is not repeatedly transmitted. 7. The method of claim 6,
The random access channel preamble for repeated transmission of Msg3 is,
A method for determining whether to transmit based on Reference Signal Received Power (RSRP) of the received synchronization signal. In a terminal performing a random access procedure for coverage extension,
a transmitter for transmitting a random access channel preamble for repeated transmission of Msg3 through a physical random access channel (PRACH);
a receiver for receiving a random access response (RAR) including uplink scheduling information for repeated transmission of the Msg3; and
Including a control unit for controlling the operation of the transmitter and the receiver,
The transmitter repeatedly transmits the Msg3 based on the uplink scheduling information. 12. The method of claim 11,
The random access channel preamble for repeated transmission of Msg3 is,
A terminal transmitted based on a PRACH opportunity configured separately from a PRACH opportunity when the Msg3 is not repeatedly transmitted. 12. The method of claim 11,
The random access channel preamble for repeated transmission of Msg3 is,
A terminal configured based on a different sequence distinguished from a sequence in the case where the Msg3 is not repeatedly transmitted. 12. The method of claim 11,
The random access channel preamble for repeated transmission of Msg3 is,
The terminal is configured based on a different sequence that is distinguished from the sequence when the Msg3 is not repeatedly transmitted, and is transmitted based on a PRACH opportunity configured separately from the PRACH opportunity when the Msg3 is not repeatedly transmitted. 12. The method of claim 11,
The random access channel preamble for repeated transmission of Msg3 is,
A terminal for which transmission is determined based on RSRP (Reference Signal Received Power) of the received synchronization signal. In a base station performing a random access procedure for coverage extension,
a receiver for receiving a random access channel preamble (RACH Preamble) for repeated transmission of Msg3 through a physical random access channel (PRACH);
a transmitter for transmitting a random access response (RAR) including uplink scheduling information for repeated transmission of the Msg3; and
Including a control unit for controlling the operation of the transmitter and the receiver,
The receiver repeatedly receives the Msg3 based on the uplink scheduling information. 17. The method of claim 16,
The random access channel preamble for repeated transmission of Msg3 is,
A base station received based on a PRACH opportunity configured separately from a PRACH opportunity when the Msg3 is not repeatedly transmitted. 17. The method of claim 16,
The random access channel preamble for repeated transmission of Msg3 is,
A base station configured based on a different sequence distinguished from a sequence in the case where the Msg3 is not repeatedly transmitted. 17. The method of claim 16,
The random access channel preamble for repeated transmission of Msg3 is,
A base station configured based on a different sequence differentiated from a sequence in which the Msg3 is not repeatedly transmitted, and received based on a PRACH opportunity configured separately from a PRACH opportunity in a case in which the Msg3 is not repeatedly transmitted. 17. The method of claim 16,
The random access channel preamble for repeated transmission of Msg3 is,
A base station in which transmission is determined based on RSRP (Reference Signal Received Power) of the received synchronization signal.

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